The present invention relates generally to a liquid crystal display panel and a method of manufacturing the same, and more particularly to a method of manufacturing a liquid crystal display panel in which a warp in each of glass substrates of the liquid crystal display panel can be avoided to suppress display unevenness.
With reference to the drawings, an explanation will be made on a conventional liquid crystal display panel or cell.
FIG. 8A is a cross sectional view illustrating a schematic structure of a conventional liquid crystal display panel, and FIG. 8B is a cross sectional view illustrating a schematic structure of a polarizer film used in the conventional liquid crystal display panel.
As shown in FIG. 8A, the conventional liquid crystal display panel 120 comprises a liquid crystal substrate assembly 110, and a pair of polarizer films 101a and 101b respectively stuck on both sides of the liquid crystal substrate assembly 110. The liquid crystal assembly 110 has a pair of glass substrates 102a and 102b. The glass substrates 102a and 102b are opposed to each other, and mutually joined via a sealing material portion 103a. Between the glass substrates 102a and 102b, there are disposed gap material portions or spacers not shown in the drawing. Also, the space between the glass substrates 102a and 102b is filled with a liquid crystal material. In FIG. 8A, a portion between the glass substrates 102a and 102b into which the liquid crystal material is injected is schematically shown as a liquid crystal layer 103.
Each of the polarizer films 101a and 101b comprises a film made of stretched polyvinyl alcohol into which iodine is doped or impregnated. Such film is hereafter called a PVA film or a PVA layer.
FIG. 8B is a cross sectional view illustrating a schematic structure of a polarizer film which is used in a conventional liquid crystal display panel and which is in a condition before sticking on the liquid crystal substrate assembly.
As shown in FIG. 8B, the polarizer film 101a on the side of a display surface has a multilayer structure which comprises, from the side of the surface stuck on the liquid crystal substrate assembly 110, a separator 104, a glue or adhesive layer 105, a triacetyle cellulose (TAC) layer 106a, a PVA layer 107, a TAC layer 106b, an antiglare (AG) layer 108, and a protective film 109. Also, the polarizer film 101b on the side of a backlight source has a structure similar to that of the polarizer film 101a shown in FIG. 8B, except that the AG layer 108 is not provided. Therefore, a detailed description on the polarizer film 101b is omitted here.
In the polarizer film 107a shown in FIG. 8B, the TAC layers 106a and 106b are stuck on both surfaces of the PVA layer 107 as a polarizer, and function as protective layers of the PVA layer 107. The protective layers of the PVA layer 107, that is, the TAC layers 106a and 106b, are provided for preventing the PVA layer 107 which is water-soluble from absorbing moisture in the air and from becoming much deteriorated thereby. As a material for the protective films of the PVA layer, triacetyle cellulose (TAC) is often used. The TAC film has a high transparency, and has superior optical isotropy. Considering these points, in the polarizing film of a liquid crystal display panel, the TAC film is a preferred material for a protective film of the PVA layer.
On the surface of the TAC layer 106a, which surface is to be stuck on the glass substrate 102a or 102b, there is formed a glue or adhesive layer 105. Further, a separator 104 is stuck on the adhesive layer 105. The separator 104 is used for protecting the adhesive layer 105 and is peelable therefrom.
Also, on the surface of the TAC layer 106b, which surface is opposite to the PVA layer 107, the AG layer 108 made of acrylic resin containing silicon particles is provided. Further, a protective film 109 for protecting the whole area of the polarizer film is stuck on the AG layer 108.
In the above-mentioned structure, the polarizer films 101a and 101b easily deform, that is, contract, due to heat treatment and the like. If the polarizer films 101a and 101b deform, each of the glass substrates 102a and 102b warps, and a gap between the glass substrates 102a and 102b varies depending on the location thereof. Thereby, there is a possibility of occurrence of deterioration or unevenness of a contrast ratio and brightness, and/or coloring in the liquid crystal display portion, that is, there is a possibility of occurrence of display unevenness. In the conventional liquid crystal display, such display unevenness caused the deterioration of display quality, display performance and reliability.
Especially, recently, the size of the display panel of the liquid crystal display has become large, and accordingly an optical film having a large area is used as a polarizer film. When the optical film having a large area is used as the polarizer film, the polarizer film is deformed more easily than the polarizer film constituted of the optical film having a smaller area, and a warp in the glass substrate and display unevenness caused by the deformation of the polarizer film appear remarkably.
Therefore, the deterioration of display performance, display quality and reliability caused by the deformation of the polarizer film was a large obstacle to the realization of a liquid crystal display having a large size.
In Japanese patent laid-open publication No. 59-226324, there is disclosed a method of sticking a polarizer film of a liquid crystal display panel. In the method disclosed in Japanese patent laid-open publication No. 59-226324, after sticking the polarizer films on a liquid crystal display panel, the liquid crystal display panel is disposed in a pressure vessel. Then, the liquid crystal display panel is pressurized in the air while heating the liquid crystal display panel at a particular temperature.
In the method disclosed in Japanese patent laid-open publication No. 59-226324, it is possible to easily remove minute bubbles produced between the polarizer films and the liquid crystal display panel when the polarizer films are stuck on the liquid crystal display panel.
However, in the method disclosed in Japanese patent laid-open publication No. 59-226324, during a heating process after sticking the polarizer films, the polarizer films, especially the TAC layers, contract or deform, and thereby a stress is produced in each of the polarizer films. By this stress, glass substrates of a liquid crystal display panel warp and the liquid crystal display panel itself deforms. Thereby, display unevenness, deterioration of a manufacturing yield and an increase in manufacturing costs are caused.
Therefore, in the conventional structures and methods, disadvantages of display unevenness caused by the deformation of the polarizer films in the liquid crystal display portion, and of deterioration of display performance, display quality and reliability of display were not obviated.
Therefore, it is an object of the present invention to obviate the disadvantages of the conventional liquid crystal display panel and the conventional method of manufacturing the same.
It is another object of the present invention to provide a liquid crystal display panel and a method of manufacturing the same in which deformation or contraction of polarizer films in a liquid crystal display panel can be suppressed.
It is still another object of the present invention to provide a liquid crystal display panel and a method of manufacturing the same in which a warp of glass substrates in a liquid crystal display panel can be suppressed.
It is still another object of the present invention to provide a liquid crystal display panel and a method of manufacturing the same in which display unevenness in a liquid crystal display panel can be suppressed.
It is still another object of the present invention to provide a liquid crystal display panel and a method of manufacturing the same in which deformation or contraction of polarizer films and a warp of glass substrates in a liquid crystal display panel can be avoided and, thereby, display unevenness can be suppressed.
It is still another object of the present invention to provide a liquid crystal display panel and a method of manufacturing the same in which display performance, display quality and reliability of a liquid crystal display can be improved.
It is still another object of the present invention to provide a liquid crystal display panel and a method of manufacturing the same in which manufacturing yield of a liquid crystal display can be improved and manufacturing cost thereof can be reduced.
According to an aspect of the present invention, there is provided a method of manufacturing a liquid crystal display panel comprising: preparing at least one polarizer films each having at least a polyvinyl alcohol layer and a triacetyle cellulose layer; preparing a liquid crystal substrate assembly which comprises a first glass substrate and a second glass substrate and a liquid crystal material disposed between the first glass substrate and the second glass substrate; heating the at least one polarizer films at a predetermined temperature for a predetermined time in a first heat treatment process; and sticking the at least one polarizer films on at least one of the first and second glass substrates, after performing the first heat treatment process.
Thereby, the contraction of the polarizer films caused by the contraction of the triacetyle cellulose (TAC) layer can be suppressed, and a warp in the glass substrates caused by the contraction of the polarizer films is also suppressed. Therefore, it is possible to suppress occurrence of display unevenness or display defects in a liquid crystal display panel or a liquid crystal display.
In this case, it is preferable that the method further comprises: after sticking the at least one polarizer films on at least one of the first and second glass substrates, heating the liquid crystal substrate assembly in which the at least one polarizer films are stuck on at least one of the first and second substrates, at a predetermined temperature for a predetermined time in a second heat treatment process.
Thereby, it becomes possible to remove minute bubbles or voids between the polarizer films and the glass substrates produced when the polarizer films are stuck on the glass substrates.
It is also preferable that the accuracy of flatness of the first and second glass substrates after the second heat treatment process is controlled to become equal to or higher than a predetermined value.
Thereby, a warp in the glass substrates of the liquid crystal display panel can be suppressed, so that it becomes possible to appropriately avoid display unevenness or display defects in the liquid crystal display panel or in the liquid crystal display.
It is further preferable that the rate of warp of the first and second glass substrates after performing the second heat treatment process is controlled to become equal to or smaller than a predetermined value.
Thereby, a warp in the glass substrates of the liquid crystal display panel can be suppressed, so that it becomes possible to appropriately avoid display unevenness or display defects in the liquid crystal display panel or in the liquid crystal display.
It is advantageous that the difference between a gap between the first and second glass substrates at the central portion of the liquid crystal display panel and a gap between the first and second glass substrates at the outermost portion of the liquid crystal display panel after performing the second heat treatment process is controlled to become substantially equal to or smaller than 0.2 xcexcm.
By controlling the above-mentioned difference in this way, it is possible to avoid display unevenness or display defect appropriately, regardless of the sizes of the polarizer film, that is, the sizes of the liquid crystal display panel.
It is also advantageous that the rate of moisture reduction of the at least one polarizer films in the first heat treatment process is controlled to become equal to or larger than a predetermined value.
Thereby, contraction of the polarizer films after sticking them on the liquid crystal substrate assembly, especially contraction of the TAC layers of the polarizer films, can be easily and appropriately suppressed. Therefore, a warp in the glass substrates of the liquid crystal display panel can be avoided, so that it becomes possible to appropriately suppress display unevenness or display defects in the liquid crystal display panel or in the liquid crystal display.
It is further advantageous that the rate of moisture reduction of the at least one polarizer films in the first heat treatment process is controlled to become equal to or larger than a predetermined value which depends on the size of the at least one polarizer film.
Thereby, regardless of the sizes of the the polarizer films, it is possible to easily and appropriately avoid deformation and warp in the glass substrates, so that it becomes possible to suppress display unevenness or display defects in the liquid crystal display panel or in the liquid crystal display.
It is preferable that the rate of moisture reduction of the at least one polarizer films in the first heat treatment process is controlled to become equal to or larger than a predetermined value which depends on the size of the at least one polarizer film, by controlling the heating temperature and/or the heating time of the first heat treatment process.
It is also preferable that the at least one polarizer films comprise a first polarizer film and a second polarizer film; and wherein, in the sticking the at least one polarizer films on at least one of the first and second glass substrates after the first heat treatment process, the first polarizer film is stuck on the first glass substrate and the second polarizer film is stuck on the second glass substrate.
It is further preferable that the rate of moisture reduction of the at least one polarizer films in the first heat treatment process is controlled to become equal to or larger than a predetermined value which depends on the size of the at least one polarizer film, thereby the accuracy of flatness of the first and second glass substrates after the second heat treatment process is controlled to become equal to or higher than a predetermined value.
It is advantageous that the rate of moisture reduction of the at least one polarizer films in the first heat treatment process is controlled to become equal to or larger than a predetermined value which depends on the size of the at least one polarizer film, thereby the rate of warp of the first and second glass substrates after the second heat treatment process is controlled to become equal to or smaller than a predetermined value.
It is also advantageous that the rate of moisture reduction of the at least one polarizer films in the first heat treatment process is controlled to become equal to or larger than a predetermined value which depends on the size of the at least one polarizer film, thereby the difference between a gap between the first and second glass substrates at the central portion of the liquid crystal display panel and a gap between the first and second glass substrates at the outermost portion of the liquid crystal display panel after the second heat treatment process is controlled to become substantially equal to or smaller than 0.2 xcexcm.
According to another-aspect of the present invention, there is provided a liquid crystal display panel comprising: a first glass substrate and a second glass substrate opposed to each other; a liquid crystal material filling the space between the first and second glass substrates; a first polarizer film which is disposed on the outside surface of the first glass substrate and which comprises at least a polyvinyl alcohol layer and a triacetyle cellulose layer; and a second polarizer film which is disposed on the outside surface of the second glass substrate and which comprises at least a polyvinyl alcohol layer and a triacetyle cellulose layer; wherein the first and second polarizer films being stuck on the first and second glass substrates, respectively, after heating the first and second polarizer films at a predetermined temperature and for a predetermined time.
Thereby, the contraction of the polarizer films caused by the contraction of the triacetyle cellulose (TAC) layer can be suppressed, and a warp in the glass substrates caused by the contraction of the polarizer films is also suppressed. Therefore, it is possible to suppress occurrence of display unevenness or display defects in a liquid crystal display panel or a liquid crystal display.
In this case, it is preferable that the liquid crystal display panel is heated at a predetermined temperature and for a predetermined time, after sticking the first and second polarizer films on the first and second glass substrates, respectively.
Thereby, it becomes possible to remove minute bubbles or voids between the polarizer films and the glass substrates produced when the polarizer films are stuck on the glass substrates.
It is also preferable that the accuracy of flatness of the first and second glass substrates is controlled to become equal to or higher than a predetermined value.
Thereby, a warp in the glass substrates of the liquid crystal display panel can be suppressed, so that it becomes possible to appropriately avoid display unevenness or display defects in the liquid crystal display panel or in the liquid crystal display.
It is further preferable that the rate of warp of the first and second glass substrates is controlled to become equal to or smaller than a predetermined value.
Thereby, a warp in the glass substrates of the liquid crystal display panel can be suppressed, so that it becomes possible to appropriately avoid display unevenness or display defects in the liquid crystal display panel or in the liquid crystal display.
It is advantageous that the difference between a gap between the first and second glass substrates at the central portion of the liquid crystal display panel and a gap between the first and second glass substrates at the outermost portion of the liquid crystal display panel is controlled to become substantially equal to or smaller than 0.2 xcexcm.
By controlling the above-mentioned difference in this way, it is possible to avoid display unevenness or display defect appropriately, regardless of the sizes of the polarizer film, that is, the sizes of the liquid crystal display panel.
It is also advantageous that the rate of moisture reduction of the first and second polarizer films when the first and second polarizer films are heated at a predetermined temperature and for a predetermined time before sticking the first and second polarizer films on the first and second glass substrates, respectively, is controlled to become equal to or larger than a predetermined value.
Thereby, contraction of the polarizer films after sticking them on the liquid crystal substrate assembly, especially contraction of the TAC layers of the polarizer films, can be easily and appropriately suppressed. Therefore, a warp in the glass substrates of the liquid crystal display panel can be avoided, so that it becomes possible to appropriately suppress display unevenness or display defects in the liquid crystal display panel or in the liquid crystal display.
It is further advantageous that the rate of moisture reduction of the first and second polarizer films when the first and second polarizer films are heated at a predetermined temperature and for a predetermined time before sticking the first and second polarizer films on the first and second glass substrates, respectively, is controlled to become equal to or larger than a predetermined value which depends on the size of the first and second polarizer films.
Thereby, regardless of the sizes of the polarizer films, it is possible to easily and appropriately avoid deformation and warp in the glass substrates, so that it becomes possible to suppress display unevenness or display defects in the liquid crystal display panel or in the liquid crystal display.
It is also preferable that the rate of moisture reduction of the first and second polarizer films is controlled to become equal to or larger than a predetermined value, by controlling the heating temperature and/or the heating time when the first and second polarizer films are heated at a predetermined temperature and for a predetermined time before sticking the first and second polarizer films on the first and second glass substrates, respectively.